If you move Saldana outside of the ring of runes towards the entrance to the room, you can effectively avoid having to the kill Entweihter Geist throughout the encounter and focus all DPS on her. You will have to dodge Dolchsturz when they spawn, but the range for each is only 4 yards, so it is easy to avoid.Entweihter Geists are adds that walk slowly towards the boss during Dunkle Kommunion, and will heal and buff the boss if they reach her before her channel of Dunkle Kommunion is complete (it is 20 seconds long). If the add DOES NOT reach her by the end of the cast, it despawns!

Position a player inside the circle of runes to be positioned to deal with the add when it spawns.

During Leerenverwüstung, when purple pools spawn all over the ground and must be avoided, the use of the reflective abilities can put a MASSIVE DoT on the boss, thus shortening the encounter significantly.

To execute this, when Knochenritual starts, the shaman should use (or the hunter use Abschreckung) and then that player should STAND IN the purple ground effect behind the Knochenritual skeleton. This will reflect the damage onto that add, thus clearing a space for your group WITHOUT even attacking it at all! Keep in mind that the add will take a few seconds to die, as it needs to take a couple ticks of damage.

As Knochenritual comes every 50-55 seconds or so, a hunter can handle two consecutive rituals, and a third if is talented (if Abschreckung is used early in the first Knochenritual, it should be off CD late in the third one). A shaman can handle every Knochenritual phase even with a glyphed .Note: In theory, this should also work with Zauberreflexion/Massenzauberreflexion, although I haven't tested it. The uncertainty lies in the fact that 2 ticks of damage are required to kill the Knochenritual add, so this ability may not be enough.

The WeakAura at the bottom of this post can be used to more easily track when is active. It can be modified for other abilities.

TL;DR: Reflect the purple swirls of death during Knochenritual to kill the adds and clear space very easily.

Below I've listed a WeakAura string that can be used to notify you when is active. It can be modified for use with other spells.